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What Is Hemophilia B?

Summary

Hemophilia is a genetic disorder caused by missing or dysfunctional proteins, called factors, that are responsible for clotting blood and preventing excessive bleeding.

There are two main types of hemophilia — hemophilia A and hemophilia B. Although the two types have very similar signs and symptoms, they are caused by mutations in different genes. Hemophilia B, the topic of this article, is the result of a genetic mutation (change in a gene) that affects the functioning of clotting factor IX.

People with hemophilia are susceptible to bruising and prolonged bleeding after injuries and particularly during and after surgical procedures [1]. In severe cases, continuous bleeding can happen after very minor trauma and sometimes in the absence of injury.

The primary method of treatment for hemophilia B is providing the necessary clotting factors intravenously or topically to wounds.

Recommended care

You should visit your primary care physician who will refer you to a hemophilia treatment center. Treatment is with medication and avoidance of trauma that can cause uncontrollable bleeding.

Hemophilia B Symptoms

As discussed, the primary symptom of hemophilia B is prolonged and/or spontaneous bleeding. However, the extent of bleeding and symptoms will vary depending on the level of factor IX. If your clotting-factor level is only mildly reduced, bleeding may occur only after surgery or significant trauma. However, if the deficiency is severe one may experience bleeding at random times in the absence of trauma.

Hemophilia B Causes

Hemophilia B is caused by genetic mutations that are most commonly passed from parent to offspring. However, about one-third of cases are caused by spontaneous mutations, meaning there is not a component of inheritance to the development of the disease [2].

How this condition is inherited

Hemophilia B is inherited in an X-linked recessive pattern and most commonly happens in males because the defective gene is passed via the mother's X chromosome. Since females inherit two X chromosomes, if one of the X chromosomes is defective, the normal X chromosome can still make a normally functioning gene and protein. However, since males only have one X chromosome, if it is defective there is no normal X chromosome to compensate. In addition to this, a characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

Why females are likely to be carriers

Though females rarely display the full disease and its symptoms, they can be carriers. Carriers are women who have one altered X chromosome. Carrier females usually have about half the amount of factor IX and are usually without symptoms. However, in some cases, carrier women have less than half the normal amount of factor IX. These individuals are at higher risk for abnormal bleeding than the general population.

How common is this condition

According to the US Centers for Disease Control and Prevention (CDC), hemophilia occurs in approximately 1 in 5,000 live births [3]. There are about 20,000 people with hemophilia in the United States, and it can affect all races and ethnic groups. Hemophilia B is about 1/4th as common as hemophilia A [4].

Treatment Options and Prevention for Hemophilia B

The main treatment for hemophilia B involves receiving a replacement of the clotting factor IX, given through a IV placed in a vein.

These treatments can be done regularly as part of a schedule to maintain factor IX levels and prevent bleeding episodes, or these injections can be used as an emergent treatment for an acute bleeding episode [5].

Other treatments

There are also other therapies for hemophilia B, which include:

Desmopressin (DDAVP): DDAVP is a hormone that can stimulate the body to release more clotting factor, and is often used in milder cases of hemophilia B.

Clot-preserving medications (antifibrinolytics): These medications, that help prevent clots from breaking down, help the limited clotting factor an individual does have work less.

Fibrin sealants: These medications can be applied directly to wound sites to promote clotting and healing. Fibrin sealants are especially useful after dental procedures.

First aid for minor cuts: Using pressure and a bandage will generally take care of the bleeding. For small areas of bleeding beneath the skin, use an ice pack. Ice pops can be used to slow down minor bleeding in the mouth.

Complications

Bleeding that can occur in hemophilia is dangerous in many ways due to the complications that can arise [6]. Complications of hemophilia B include:

Bleeding into the brain: A moderate bump on the head can cause bleeding into the brain. Though this is a rare occurrence, it is one of the most serious complications of hemophilia B.

Deep internal bleeding: Bleeding that occurs in the deep muscles of the body can result in limb swelling and can compress nerves, leading to numbness or pain.

Joint damage: Internal bleeding can also put pressure on the joints, especially the knees, causing severe pain. Bleeding into the knee joint is called hemarthrosis, and if untreated may cause arthritis or physical destruction to the joint.

Infection: People with hemophilia are more likely to have blood transfusions, increasing their risk of receiving contaminated blood products. Blood products became far safer after the mid-1980s due to the screening of donated blood for hepatitis and HIV [7].

Adverse reaction to clotting factor treatment: In some people with hemophilia, the immune system has a reaction to the clotting factors used to treat bleeding. When this happens, the immune system develops proteins (inhibitors) that inactivate the clotting factors, making treatment less effective.

When to Seek Further Consultation for Hemophilia B

If you have hemophilia B and experience any of the symptoms below, call 911 immediately. These may be signs of serious bleeding in the brain:

Painful, prolonged headache

Repeated vomiting

Sleepiness or lethargy

Double vision

Sudden weakness or clumsiness

Convulsions or seizures

In addition, if you experience an injury where the bleeding will not stop or your joints become painful, swollen, or warm to the touch, seek medical attention promptly as well.

Questions Your Doctor May Ask to Determine Hemophilia B

To diagnose this condition, your doctor would likely ask about the following symptoms and risk factors.